Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat.
Add the minced garlic andsauté until fragrant, about 30 seconds.
Add the shredded cabbage, carrots, bean sprouts, and bell peppers. Stir-fry for 3-4 minutes until the vegetables are tender but still crisp.
If using, add the cooked chicken or shrimp to the skillet and mix well.
Stir in the soy sauce,oyster sauce (if using), and sesame oil. Cook for an additional 2 minutes,ensuring the ingredients are well combined.
Remove the skillet from heat and let the filling cool slightly.